Analysis of Maximum Extractable Power of Single-Frequency ${\rm Yb}^{3+}$-Doped Phosphate Fiber Sources

We analyze the physical limits on the maximum extractable power of the single-frequency Yb
³⁺
-doped phosphate fiber lasers and amplifiers. Our analysis indicates that the maximum extractable power of the single-frequency Yb
³⁺
-doped phosphate fiber sources are limited by pump brightness, optical damage, melt of the core, stimulated Brillouin scattering (SBS) and thermal lens, and among which SBS and thermal lens become the primary physical limits. As a result of these limitations, the single-frequency Yb
³⁺
-doped phosphate fiber sources have a maximum extractable power of 2.02 kW at the optimum fiber length of 68 cm. We also show that the single-frequency Yb
³⁺
-doped phosphate fiber sources will produce much higher power than the silica fiber sources if the fibers have the same core diameter. The maximum extractable power of the strictly single-mode single-frequency Yb
³⁺
-doped phosphate fiber sources is up to 1.1 kW, which is almost six times as high as that of analogous silica fiber sources.